The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A typical multi-speed automatic transmission uses a combination of torque transmitting devices, such as clutches or brakes, to achieve a plurality of forward and reverse gear or speed ratios as well as a Neutral and a Park. Selection of speed ratios is typically accomplished by a microprocessor transmission control module that employs various vehicle parameters, for example vehicle speed, and various driver input signals, for example accelerator pedal position, to select the appropriate speed ratios. The transmission then engages a combination of the toque transmitting devices to provide the desired speed ratios.
One type of automatic transmission is the dual clutch transmission. The dual clutch transmission includes a dual clutch that selects between even gear ratios and odd gear ratios. Dual clutches may be either wet or dry. Dry dual clutches are actuated using diaphragm springs, i.e. compliant levers. If the levers are compliant, the stroke required at the clutch is multiplied by the compliant lever and the multiplication factor is a function of the lever ratio and the compliance of the lever. Hence the resultant stroke to be produced at the lever actuation point is high. When this actuation is controlled by a hydraulic system, the required volume of fluid required is also high since the actuation stroke is high. It is well known that when the fluid flow is very high, it can be difficult to accurately control the fluid pressure simultaneously. In addition, the force at the clutch and the torque transmitted through the clutch can be related to the position of the lever actuation point. Therefore, in a compliant lever system, the hydraulic actuation is controlled by a closed loop position control system using position sensors at the actuation point and flow control solenoids. These components make the system expensive and complicated. Therefore, there is room in the art for a dual clutch actuation system that offers pressure control at the actuation point, that reduces the variation between pressure commanded and the force that is actually applied to the clutches thereby providing more precise control, that increases the response time of the system by eliminating flexible springs or diaphragms that add dynamic delays to the system, and that eliminates the need for closed loop pressure control.